Mechanistic interaction study of thin oxide dielectric with conducting organic electrode

Abstract

This paper aims at understanding the interaction of intrinsic conducting polymer, PEDT, with ALD-deposited Al2O3 and thermally oxidized Ta2O5 dielectrics, and the underlying mechanisms for increase in leakage currents in PEDT-based capacitors. Conducting polymers offer several advantages as electrodes for high surface area capacitors because of their lower resistance, self-healing and enhanced conformality. However, capacitors with in situ polymerized PEDT show poor electrical properties that are attributed to the interfacial interaction between the organic electrode and the oxide dielectric. This study focuses on characterizing these interactions. A combination of compositional, structural and electrical characterization techniques was applied to polymer-solid-state-capacitor to understand the interfacial chemical behavior and dielectric property deterioration of alumina and tantalum-oxide films. XPS and impedance studies were employed to understand the stiochiometric and compositional changes that occur in the dielectric film on interaction with in situ deposited PEDT. Based on the observations from several complimentary techniques, it is concluded that tantalum-pentoxide has more resistance towards chemical interaction with in situ polymerized PEDT. The thermally oxidized Ta2O5-PEDT system showed leakage current of 280nAμF−1 at 3V with a breakdown voltage of 30V. On the other hand, Al2O3-PEDT capacitor showed leakage current of 50μAμF−1 and a breakdown voltage of 40V. The study reports direct evidence for the mechanism of resistivity drop in alumina dielectric with in situ polymerized PEDT electrode.